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KASAN: slab-out-of-bounds Read in cache_seq_start_rcu

Status: upstream: reported C repro on 2026/04/21 15:34
Subsystems: net nfs
Labels: prio:high
[Documentation on labels]
Reported-by: syzbot+60cfa08822470bbebe44@syzkaller.appspotmail.com
First crash: 21d, last: 17h58m
▶ ▼ ✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision Error
bfbd0935-ecf4-43b9-b1d9-769e9634a875 assessment-security DenialOfService: ✅ Exploitable: ✅ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ✅ VMGuestTrigger: ❌ VMHostTrigger: ❌ ✅ KASAN: slab-out-of-bounds Read in cache_seq_start_rcu 2026/04/28 06:18 2026/04/28 06:19 2026/04/28 08:05 ce741359ce23515704db594be00c4c776239ee22
▶ ▼ Discussions (2)
Title Replies (including bot) Last reply
[PATCH] net: sunrpc: fix slab-out-of-bounds read in cache_seq_start_rcu 2 (2) 2026/04/28 13:56
[syzbot] [net?] [nfs?] KASAN: slab-out-of-bounds Read in cache_seq_start_rcu 2 (5) 2026/04/21 18:41
▶ ▼ Last patch testing requests (2)
Created Duration User Patch Repo Result
2026/04/21 16:24 30m aha310510@gmail.com patch upstream OK log
2026/04/21 16:23 1h25m aha310510@gmail.com patch upstream OK log

Sample crash report:
==================================================================
BUG: KASAN: slab-out-of-bounds in __cache_seq_start net/sunrpc/cache.c:1351 [inline]
BUG: KASAN: slab-out-of-bounds in cache_seq_start_rcu+0x3fe/0x420 net/sunrpc/cache.c:1399
Read of size 8 at addr ffff88802ae92800 by task syz.0.17/6044

CPU: 1 UID: 0 PID: 6044 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0x13d/0x4b0 mm/kasan/report.c:482
 kasan_report+0xdf/0x1d0 mm/kasan/report.c:595
 __cache_seq_start net/sunrpc/cache.c:1351 [inline]
 cache_seq_start_rcu+0x3fe/0x420 net/sunrpc/cache.c:1399
 seq_read_iter+0x2c1/0x1270 fs/seq_file.c:226
 seq_read+0x33b/0x4c0 fs/seq_file.c:163
 pde_read fs/proc/inode.c:308 [inline]
 proc_reg_read+0x240/0x330 fs/proc/inode.c:320
 vfs_read+0x1e4/0xb30 fs/read_write.c:572
 ksys_pread64 fs/read_write.c:765 [inline]
 __do_sys_pread64 fs/read_write.c:773 [inline]
 __se_sys_pread64 fs/read_write.c:770 [inline]
 __x64_sys_pread64+0x1eb/0x250 fs/read_write.c:770
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x10b/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f88b8d9c819
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffc567f4a98 EFLAGS: 00000246 ORIG_RAX: 0000000000000011
RAX: ffffffffffffffda RBX: 00007f88b9015fa0 RCX: 00007f88b8d9c819
RDX: 0000000000000566 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 00007f88b8e32c91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000080000002 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f88b9015fac R14: 00007f88b9015fa0 R15: 00007f88b9015fa0
 </TASK>

Allocated by task 5958:
 kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
 kasan_save_track+0x14/0x30 mm/kasan/common.c:78
 poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
 __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:415
 kasan_kmalloc include/linux/kasan.h:263 [inline]
 __do_kmalloc_node mm/slub.c:5295 [inline]
 __kmalloc_noprof+0x301/0x850 mm/slub.c:5307
 kmalloc_noprof include/linux/slab.h:954 [inline]
 kzalloc_noprof include/linux/slab.h:1188 [inline]
 cache_create_net+0xa2/0x1f0 net/sunrpc/cache.c:1733
 nfsd_export_init+0x62/0x250 fs/nfsd/export.c:1536
 nfsd_net_init+0x69/0x3e0 fs/nfsd/nfsctl.c:2209
 ops_init+0x1e2/0x5f0 net/core/net_namespace.c:137
 setup_net+0x118/0x3a0 net/core/net_namespace.c:446
 copy_net_ns+0x46f/0x7c0 net/core/net_namespace.c:579
 create_new_namespaces+0x3ea/0xac0 kernel/nsproxy.c:132
 unshare_nsproxy_namespaces+0xf2/0x220 kernel/nsproxy.c:234
 ksys_unshare+0x438/0xab0 kernel/fork.c:3245
 __do_sys_unshare kernel/fork.c:3319 [inline]
 __se_sys_unshare kernel/fork.c:3317 [inline]
 __x64_sys_unshare+0x31/0x40 kernel/fork.c:3317
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x10b/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88802ae92000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 0 bytes to the right of
 allocated 2048-byte region [ffff88802ae92000, ffff88802ae92800)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2ae90
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88813fe86000 dead000000000100 dead000000000122
raw: 0000000000000000 0000000800080008 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88813fe86000 dead000000000100 dead000000000122
head: 0000000000000000 0000000800080008 00000000f5000000 0000000000000000
head: 00fff00000000003 fffffffffffffe01 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5958, tgid 5958 (syz-executor), ts 108313513495, free_ts 108309100167
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x153/0x170 mm/page_alloc.c:1858
 prep_new_page mm/page_alloc.c:1866 [inline]
 get_page_from_freelist+0x11a6/0x33b0 mm/page_alloc.c:3946
 __alloc_frozen_pages_noprof+0x27c/0x2bc0 mm/page_alloc.c:5226
 alloc_slab_page mm/slub.c:3278 [inline]
 allocate_slab mm/slub.c:3467 [inline]
 new_slab+0xa6/0x6c0 mm/slub.c:3525
 refill_objects+0x277/0x420 mm/slub.c:7251
 refill_sheaf mm/slub.c:2816 [inline]
 __pcs_replace_empty_main+0x375/0x650 mm/slub.c:4651
 alloc_from_pcs mm/slub.c:4749 [inline]
 slab_alloc_node mm/slub.c:4883 [inline]
 __kmalloc_cache_noprof+0x493/0x6f0 mm/slub.c:5410
 kmalloc_noprof include/linux/slab.h:950 [inline]
 netdev_create_hash net/core/dev.c:12922 [inline]
 netdev_init+0x151/0x3c0 net/core/dev.c:12942
 ops_init+0x1e2/0x5f0 net/core/net_namespace.c:137
 setup_net+0x118/0x3a0 net/core/net_namespace.c:446
 copy_net_ns+0x46f/0x7c0 net/core/net_namespace.c:579
 create_new_namespaces+0x3ea/0xac0 kernel/nsproxy.c:132
 unshare_nsproxy_namespaces+0xf2/0x220 kernel/nsproxy.c:234
 ksys_unshare+0x438/0xab0 kernel/fork.c:3245
 __do_sys_unshare kernel/fork.c:3319 [inline]
 __se_sys_unshare kernel/fork.c:3317 [inline]
 __x64_sys_unshare+0x31/0x40 kernel/fork.c:3317
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x10b/0xf80 arch/x86/entry/syscall_64.c:94
page last free pid 5958 tgid 5958 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1402 [inline]
 __free_frozen_pages+0x747/0x1040 mm/page_alloc.c:2943
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x47/0xf0 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x1a0/0x1f0 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x69/0x90 mm/kasan/common.c:350
 kasan_slab_alloc include/linux/kasan.h:253 [inline]
 slab_post_alloc_hook mm/slub.c:4569 [inline]
 slab_alloc_node mm/slub.c:4898 [inline]
 kmem_cache_alloc_node_noprof+0x25a/0x6f0 mm/slub.c:4950
 __alloc_skb+0x140/0x710 net/core/skbuff.c:702
 alloc_skb include/linux/skbuff.h:1383 [inline]
 nlmsg_new include/net/netlink.h:1055 [inline]
 netlink_ack+0x117/0xb80 net/netlink/af_netlink.c:2487
 netlink_rcv_skb+0x333/0x420 net/netlink/af_netlink.c:2556
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x585/0x850 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x8b0/0xda0 net/netlink/af_netlink.c:1894
 sock_sendmsg_nosec net/socket.c:787 [inline]
 __sock_sendmsg net/socket.c:802 [inline]
 __sys_sendto+0x468/0x4b0 net/socket.c:2265
 __do_sys_sendto net/socket.c:2272 [inline]
 __se_sys_sendto net/socket.c:2268 [inline]
 __x64_sys_sendto+0xe0/0x1c0 net/socket.c:2268
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x10b/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff88802ae92700: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff88802ae92780: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88802ae92800: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                   ^
 ffff88802ae92880: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88802ae92900: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

Crashes (42):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/04/21 13:10 upstream b4e07588e743 3f2e655b .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Read in cache_seq_start_rcu
2026/04/21 12:01 upstream b4e07588e743 3f2e655b .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Read in cache_seq_start_rcu
2026/04/21 09:18 upstream b4e07588e743 3f2e655b .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Read in cache_seq_start_rcu
2026/04/21 08:04 upstream b4e07588e743 3f2e655b .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Read in cache_seq_start_rcu
2026/05/11 21:53 upstream 5d6919055dec d168f260 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Read in cache_seq_start_rcu
2026/05/11 18:15 upstream 5d6919055dec 845acb1c .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Read in cache_seq_start_rcu
2026/05/11 13:27 upstream 5d6919055dec 845acb1c .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Read in cache_seq_start_rcu
2026/05/11 00:35 upstream aa54b1d27fe0 29233ece .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Read in cache_seq_start_rcu
2026/05/10 16:40 upstream 1bfaee9d3351 29233ece .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Read in cache_seq_start_rcu
2026/05/10 16:18 upstream 1bfaee9d3351 29233ece .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Read in cache_seq_start_rcu
2026/05/09 18:39 upstream 70390501d194 29233ece .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Read in cache_seq_start_rcu
2026/05/09 16:02 upstream 70390501d194 29233ece .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Read in cache_seq_start_rcu
2026/05/09 03:00 upstream cbf457c584b5 29233ece .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Read in cache_seq_start_rcu
2026/05/09 02:27 upstream cbf457c584b5 29233ece .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Read in cache_seq_start_rcu
2026/05/08 17:47 upstream 917719c412c4 5633175a .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Read in cache_seq_start_rcu
2026/05/07 18:15 upstream 8ab992f815d6 0211be7b .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Read in cache_seq_start_rcu
2026/05/07 07:21 upstream adc1e5c6203c f250db59 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Read in cache_seq_start_rcu
2026/05/07 05:46 upstream adc1e5c6203c f250db59 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Read in cache_seq_start_rcu
2026/05/05 07:23 upstream c7e4e4d5f7dc a898ba9c .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Read in cache_seq_start_rcu
2026/05/05 02:31 upstream c7e4e4d5f7dc a898ba9c .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Read in cache_seq_start_rcu
2026/05/04 23:52 upstream c7e4e4d5f7dc a898ba9c .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Read in cache_seq_start_rcu
2026/05/04 06:17 upstream f377d0025eb0 a0d91488 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Read in cache_seq_start_rcu
2026/05/04 02:25 upstream f377d0025eb0 a0d91488 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Read in cache_seq_start_rcu
2026/05/03 16:56 upstream 66edb901bf87 a0d91488 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Read in cache_seq_start_rcu
2026/05/03 16:36 upstream 66edb901bf87 a0d91488 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Read in cache_seq_start_rcu
2026/05/03 14:26 upstream 66edb901bf87 a0d91488 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Read in cache_seq_start_rcu
2026/05/03 03:59 upstream 66edb901bf87 a0d91488 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Read in cache_seq_start_rcu
2026/05/02 02:52 upstream 6fe0be6dc7fa 753c55b9 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Read in cache_seq_start_rcu
2026/05/01 19:16 upstream 26fd6bff2c05 753c55b9 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Read in cache_seq_start_rcu
2026/05/01 16:59 upstream 26fd6bff2c05 753c55b9 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Read in cache_seq_start_rcu
2026/05/01 07:28 upstream 26fd6bff2c05 753c55b9 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Read in cache_seq_start_rcu
2026/04/30 21:18 upstream e75a43c7cec4 a7464baf .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Read in cache_seq_start_rcu
2026/04/30 18:04 upstream e75a43c7cec4 a7464baf .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Read in cache_seq_start_rcu
2026/04/30 03:37 upstream 57b8e2d666a3 005438fc .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Read in cache_seq_start_rcu
2026/04/29 12:29 upstream dca922e019dd 7ca9e4d8 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Read in cache_seq_start_rcu
2026/04/27 06:25 upstream 20b64cf8705a 9c2d0995 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Read in cache_seq_start_rcu
2026/04/27 04:22 upstream 20b64cf8705a 9c2d0995 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Read in cache_seq_start_rcu
2026/04/26 12:06 upstream 897d54018cc9 9c2d0995 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Read in cache_seq_start_rcu
2026/04/26 04:26 upstream 897d54018cc9 9c2d0995 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Read in cache_seq_start_rcu
2026/04/25 08:23 upstream 27d128c1cff6 9c2d0995 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Read in cache_seq_start_rcu
2026/04/23 12:16 upstream 2a4c0c11c019 b10da5ec .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Read in cache_seq_start_rcu
2026/04/21 06:55 upstream b4e07588e743 3f2e655b .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto KASAN: slab-out-of-bounds Read in cache_seq_start_rcu
* Struck through repros no longer work on HEAD.